Recently, the mainstream of manufacturing lines for the semiconductor device has a layout where a job shop system is employed. The job shop system includes a plurality of units, which are referred to as bays and bring together processing apparatuses which have the same kind of functions, and connects the bays by a conveyance robot or a belt conveyor in a large clean room.
For a work processed in the manufacturing line, a large diameter wafer which has a diameter of, for example, 12 inches is used. The manufacturing system manufactures thousands of semiconductor chips from one sheet of the wafer.
However, in this job shop system, in the case where a plurality of similar processes is repeated, a conveyance distance inside a bay and among bays becomes substantially longer and waiting time is also longer. This causes increased manufacturing time, increased products in progress, or other factors which cause an increased cost. Thus, a problem of low productivity may arise in the manufacturing line for processing a large number of works.
In view of this, a manufacturing line by a flow shop system where semiconductor processing apparatuses are arranged in the order of processes has been proposed instead of the conventional manufacturing line by the job shop system.
On the other hand, a manufacturing line by the flow shop system is the most appropriate for a case where a large number of the same products are manufactured, however, in the case where a manufacturing procedure (recipe) needs to be changed to manufacture another product, it is necessary to rearrange the location of each semiconductor processing apparatus in the manufacturing line in the order of the process flow of the work. However, considering labors and time for the rearrangement, it is not realistic to rearrange the location in that way every time the product is changed. Especially, in the current situation where a huge semiconductor processing apparatus is fixed and disposed in a clean room which is a closed space, it is realistically impossible to rearrange the semiconductor processing apparatus in each case.
In conventional semiconductor manufacturing systems, the greatest importance has been placed on simultaneous productivity (amount of production per unit time) as a factor for minimizing the manufacturing cost. Thus, an increase in the diameter of a work size (silicon wafer size) and an increase in the number of the unit of manufacturing (number of orders for one type of product) have been prioritized, and a huge manufacturing system, so-called megafab has been oriented.
In this huge manufacturing system, the number of processes is more than several hundreds. In proportion to that number, the numbers of bays and apparatuses have been also increasing substantially.
Accordingly, a facility investment of several hundreds of billions of yen is required to establish such a megafab, and an aggregate investment has been becoming huge although the throughput of the entire manufacturing line has been improving.
Furthermore, as the manufacturing system has been becoming huge as described above, the control of the apparatus has been becoming complicated. Thus, conveyance time or waiting time in a conveyance system has been dramatically increasing. Accordingly, the number of wafers in progress which remain in the manufacturing line has been also dramatically increasing. Since the unit price of the large diameter wafer used here is very high, an increase in the number of wafers in progress causes an increase in cost.
In view of this, it is said that total productivity including the facility investment has already started to decrease under present circumstances, compared with a comparatively medium-scale manufacturing line where the wafer which has a smaller diameter than the current wafer is used.
FIG. 7 illustrates a size effect of a semiconductor manufacturing system in the megafab described above.
In the case of the currently most advanced semiconductor plant (megafab) where the wafer size is 12 inches, the number of apparatuses is 300, the number of wafers in progress which stay in the system is 17000, the number of masks to be used is 34, the floor space is 20000 square meters, and the amount of the facility investment is approximately 300 billion yen.
In this case, the production capacity per month is 140 million pieces per year when converted to the chip of 1 cm2. The operation rate of the wafer is less than 1%, and the resource utilization efficiency is less than 0.1%. However, the prerequisite is as follows. The required time (cycle time) in each process is 1 minute per one wafer, the number of processes is 500 in the case of a metal 8 layer semiconductor, and the design rule is 90 nm.
On the other hand, there are needs to manufacture extremely small amount of semiconductors, for example, in several pieces to several hundreds of pieces, for an engineering sample, a ubiquitous sensor, or the like.
In the case of the manufacturing system which is not such a huge manufacturing system, this extremely small amount production can be performed such that the cost performance is not sacrificed much. However, if this extremely small amount production is performed in the manufacturing line of this huge manufacturing system, the cost performance becomes extremely low. Accordingly, another product type has to be processed in the manufacturing line at the same time.
However, if multiple product types are processed at the same time to perform a mix flow production, the productivity of the manufacturing line further decreases as the number of product types increases. In view of this, this huge manufacturing system cannot appropriately address the production for extremely small amount and multiple product types.
Regarding the device manufacturing system where the flow shop system or the job shop system is employed, various kinds of devices to address a decrease in an operation rate in the respective methods have been conventionally proposed (PATENT LITERATURE 1 or PATENT LITERATURE 2).